Die-hard fans of USA Network's
"Psych" finally get to see
"Psych: The Musical" on Sunday, Dec. 15.

For those who know
Dule Hill only from
"The West Wing," he's a smooth tap-dancer now starring on Broadway in
"After Midnight." He,
James Roday,
Timothy Omundson (who has a particularly rich baritone) and the rest of the cast also prove they can sing in the two-hour special.

"After Season 5, we were at Comic-Con, and (series creator
Steve Franks) put it out there to fans: 'Do you want a musical?' And everyone screamed," Roday tells
Zap2it. "He could have said, 'Do you want a show where we all sit in a circle and break wind?' And they would have reacted in the same way."

Franks recalls he toyed with the idea of creating a musical episode since the beginning.

"We had started on the pilot, talking about doing a musical, and it was just a weird, off-in-the-distance idea," Franks says. "We talked about it because after the last shot of the pilot, James and Dule had done a lot of singing and performed
Michael Jackson's 'Man in the Mirror.' "

In the special, Shawn and Gus (Roday and Hill) track down crazed playwright Z (guest star
Anthony Rapp, "Rent"). Z is accused of acting out every scorned playwright's fantasy -- OK, maybe only the most delusional scorned playwrights -- of burning a theater to the ground with a critic inside.

Z was institutionalized in a hospital for the criminally insane, where he had, conveniently, confided in Mr. Yang (
Ally Sheedy).

As usual, "Psych" does not take itself too seriously, and the musical does not require knowing the series' back stories.

"I designed everything I wrote in this episode, every character in a song or dialogue, every character is introduced as if this is the first time," Franks says. "If you never watched an episode of 'Psych,' this is the perfect one to get introduced."

Franks doesn't miss a beat and acknowledges that hard-core "Psych"-Os, as fans of the seventh-season show refer to themselves, will find incongruities.

"You could make a drinking game, some sort of inaccuracy within the storyline," Franks says.

"There are a whole bunch of little things, Lassie (
Omundson) not wearing a wedding ring.

'Psych' followers, "Psych"-Os, will pick up on inaccuracies, because I was working on some of this before some of that happened."

"I think it does tie up, it certainly wraps up the Yang story," Franks says.

She is killed in this episode, but that is not necessarily a spoiler. As Hill notes, on this show, death isn't definitively the end.

"Characters don't really die in 'Psych'; they just morph into a different reality," Hill says.

"That came out of me texting Steve and saying, 'How about me doing a reggae song?' " Hill says. "And the way he wove it into the story, even though I didn't get a chance to dance much, we didn't really have any extra time with the show, I can understand why we didn't have enough time to choreograph a tap number for me."

The show stayed on its regular schedule while shooting the special, which features 14 original songs. Franks credits composer Adam Cohen for taking Franks' "acoustic guitar songs and turning them into these amazing orchestral pieces, and made it into a huge, magical final piece."

The payoff for fans will be in watching actors they've long come to love revealing more talents.

"I was always in bands in high school and college, and I certainly enjoyed singing," Roday says. "I thought of myself as a dude who could sing in a pinch."

In this he sings a lot.

"All of the numbers are 'Psych' joyous," Roday says. "Yang's death scene was the one that kind of transcended the usual 'Psych' good time. Not only were we killing a character that made up her own minifranchise on the show, but we do what we do pretty well."

The best friends continue to have a truly fun rapport.

At one point, the dynamic duo sings to Yang via Skype -- from a broom closet, oddly enough -- and it works.

"She could be in Shanghai by now," Gus says.

"Please," Shawn says, "she could be all the way to China by now."

"I think it embodies 'Psych,' and I am proud that all of our music was original," Roday says. "And that we are an hour-long show, in the sense of how do you justify it, and why is it more worthy than other shows that do musicals?"

Franks was not knocking any other shows, but he had a solid vision for this from the onset.

"The second we mentioned musical, everyone said, 'What covers will you do?' (And his immediate response was): 'Oh, God, we are not going to do the covers. What is the point of that?' "